These have developed needs for polymers which can be made into transparent blue articles without additional colorants, i.e., polymers that can be made into articles which have high blueness values. There have been developed copolymers of monovinylaromatic and conjugated diene monomers which can be made into colorless transparent articles that have low blueness due at least in part to modification of the light scattering properties of the molecular structure of the polymer. But the need for copolymers by monovinylaromatic and conjugated diene monomers which can be made into attractive, clear articles with high blueness values, good impact strength and other advantageous properties is yet unfilled. The polymers satisfying these needs should be suitable for use with conventional extrusion, injection and blow molding equipment and also suitable for use in other methods of forming plastics into containers, tubes, films, fibers, and the like.
Much effort has been directed to the preparation of substantially transparent polymodal monovinylaromatic-conjugated diene block copolymer resins with a variety of block structures produced by a variety of monomer addition and initiator sequences and a variety of coupling agents. Blueness of articles formed from various monovinylaromatic-conjugated diene copolymers and blends of these copolymers with other polymers is a longstanding problem in applications where colorless materials are desirable because of the unpredictability of how much blueness will result from the multifarious polymodal structures and blends thereof. Conversely, the same unpredictability is encountered when it is desired to obtain high blueness values in the polymers to avoid subsequent use of colorants that may or may not give as attractive an appearance without loss of transparency.